This invention relates to emergency call systems and, in particular, to a technique for indicating the loss of position of an emergency call system.
Emergency Call Systems (ECS), which integrate positioning and cellular phone technology, are gaining in popularity since the introduction of the Ford RESCU system. These systems provide the driver of a suitably equipped automobile push-button access to emergency services (e.g., as can be accessed through 911 calling), as well as roadside assistance. In addition, the emergency call may be activated by airbag deployment and request emergency services even when the driver is unconscious. When the request for emergency services is made, the ECS sends positioning information supplied by the navigation system to a service center by placing a call using the ECS cellular phone.
However, except when such a request is made and the results are observed, the driver is unaware of the status of the ECS system. Such a drawback may lead to system failure if the navigation system is not performing as expected.
Referring to U.S. Pat. No. 5,479,482, an emergency messaging system is disclosed. However, such system does not address the issue of navigation solution integrity. At best, the O482 patent discloses a warning light that is lit only when a malfunction of the cellular link is detected. No indication of the integrity of the positioning solution is even considered or addressed.
Accordingly, the present invention provides an assessment, in real-time, of the integrity of the positioning solution and navigation sensors used to support an Emergency Calling System (ECS) for automotive applications. This integrity information is used, via a warning light displayed to the driver, to indicate when the system will not support Emergency Calling to the accuracies required. This indication is essential to the successful operation of the system, as loss of positioning accuracy can lead to loss of life in a worst-case scenario.